Ensaero—A multidisciplinary program for fluid/structural interaction studies of aerospace vehicles

Scattered data interpolation is an essential part of bidimensional empirical mode decomposition (BEMD) of an image. In the decomposition process, local maxima and minima of the image are extracted at each iteration and then interpolated to form the upper and the lower envelopes, respectively. The number of two-dimensional intrinsic mode functions resulting from the decomposition and their properties are highly dependent on the method of interpolation. Though a few methods of interpolation have been tested and/or applied to the BEMD process, many others remain to be tested. This paper evaluates the performance of some of the widely used surface interpolation techniques to identify one or more good choices of such methods for envelope estimation in BEMD. The interpolation techniques studied in this paper include various radial basis function interpolators and Delaunay triangulation based interpolators. The analysis is done first using a synthetic texture image and then using two different real texture images. Simulations are made to focus mainly on the effect of interpolation methods by providing less or negligible control on the other parameters or factors of the BEMD process.

Bidimensional empirical mode decomposition using various interpolation techniques

The tape placement for thermoplastic composites involves heating, melting, and cooling steps just as do the other manufacturing processes. Consequently, development of residual stresses is unavoidable due to disparate thermal characteristics of matrix and fiber materials and also due to nonuniform cooling rates. From the product quality standpoint, such as interlaminar strength, dimensional accuracy etc., these stresses should be kept within allowable limits. In this study, a thermoviscoelastic finite element model was developed to predict residual stresses induced during the placement of thermoplastic composite tapes. The process, being continuous, was considered to be under a quasi steady state where process conditions do not change with respect to the moving roller. Relaxation of the residual stresses in previously laid layers was also allowed for. Results were obtained for both unidirectional and cross-ply laminates. They show the residual stress distributions through the thickness for a number of chosen sets of process parameters (e.g., roller velocity and heat input). Therefore, residual stresses in a laminate can be controlled by modifying these process parameters.

http://journals.sagepub.com/doi/pdf/10.1177/0892705702015006207

Analysis of Process-Induced Residual Stresses in Tape Placement:

Efficient extraction of wind energy is a complex, multidisciplinary process. This paper examines common objectives used in wind turbine optimization problems. The focus is not on the specific optimized designs, but rather on understanding when certain objectives and constraints are necessary, and what their limitations are. Maximizing annual energy production, or even using sequential aero/structural optimization, is shown to be significantly suboptimal compared to using integrated aero/structural metrics. Minimizing the ratio of turbine mass to annual energy production can be effective for fixed rotor diameter designs, as long as the tower mass is estimated carefully. For variable-diameter designs, the predicted optimal diameter may be misleading. This is because the mass of the tower is a large fraction of the total turbine mass, but the cost of the tower is a much smaller fraction of overall turbine costs. Minimizing the cost of energy is a much better metric, though high fidelity in the cost modeling is as important as high fidelity in the physics modeling. Furthermore, deterministic cost of energy minimization can be inadequate, given the stochastic nature of the wind and various uncertainties associated with physical processes and model choices. Optimization in the presence of uncertainty is necessary to create robust turbine designs.

/pdf/objectives-and-constraints-for-wind-turbine-optimization-d6kfmvvig1.pdf

Objectives and Constraints for Wind Turbine Optimization

LOM is one of the techniques for rapid prototyping, which is used to build three‐dimensional solid objects. In this paper, a numerical analysis of the thermomechanical behavior of a laminate during the LOM process is presented. Models were developed to describe heat transfer and deformation phenomena. These models are incorporated into computer codes to generate numerical results. The numerical results show how the process parameters (e.g. roller temperature, velocity, indentation) are related to temperature and stress distributions within the laminate. By using this code, process conditions which are favorable to bonding are identified.

Thermomechanical analysis of the laminated object manufacturing (LOM) process

Computer program aids in reduction and analysis of data. It determines critical loading conditions for critical values of reactions, applied loads, deflections, stresses, internal loads, etc. Input to program must be in one of specified three-part format.

J. C. Long

Papers

Finite-element structural analysis